Mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) cause Cystic Fibrosis, a common lethal autosomal recessive disorder, by affecting the water/salt balance of the lungs and several other key organs. The CFTR-Associated Ligand (CAL) is a PDZ domain binding protein that binds to the C-terminus of CFTR. While it has been previously shown that CAL reduces cell surface WT-CFTR and promotes its degradation in the lysosome, CAL's interactions with ?F508-CFTR have never been characterized. The goal of this study is to illuminate how CAL regulates trafficking and degradation of ?F508-CFTR. The present proposal posits that CAL is critical for ER and post-ER trafficking of the ?F508-CFTR mutant and may be a worthwhile target for treatment in patients. The proposal is built upon two specific aims, the first of which is to elucidate to the physiological role of CAL in the early trafficking pathway of ?F508-CFTR. The second aim is focused on determining which accessory proteins, including chaperones and well known CAL interacting proteins, are influenced by or bound to CAL in the process of ?F508-CFTR regulation. Preliminary data has shown that CAL increases cell surface expression of ?F508-CFTR and is degraded in the proteasome. The research training program has been designed for successful completion of the stated aims in two years, as the student has completed all other necessary degree program requirements and already has promising preliminary data. Methods for achieving the stated goals of the research are focused on cell culture work and microscopy, both of which are easily accessible within the Johns Hopkins School of Medicine and thus are realistic in scope.